What is the truth about 5W-30 and 10W-30?

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Shannow-

If you search for "interesting article" of some time back you will find a Toyota engineering paper dated 1997 that indicated testing showed a lower limit of 2.6 cp for proper wear protection. What a surprise that Motorcraft 5-20 has a HTHS value of 2.65
I suspect that the manufacturers have been testing 5-20 for at least a few years and found it OK as far as engine life is concerned.
I have switched from M1 0-40 to Motorcraft 5-20 in my Ford.
Stay tuned for my UOA in a few months. I expect that it will show as good a result as others who have begun using this new trend in -20 engine oil and posted excellant UOA results.

And keep in mind Terry's comments on what our -30 wt oils are really like under HTHS conditions!
...seems switching from -30 to -20 wt oils may not be such a big deal after all.
 
quote:

Originally posted by Shannow:
...Is a 0W-20 with an HTHS of 2.8 equally as protective as a 10W-40 with the same HTHS ?

Economy wise, why should they be different, if their HTHS is the same ?


Economy wise, the difference will be pumping loses.

Althought as Patman pointed out, you won't find a 10w-40 that low. Maybe a 5w-30. I would say protection should be similar.
 
I'm not sure about all these X W X's either. But I put almost 300,000 miles on an 89 Grand Am 2.3 using 5W30 and have over 252,000 on a 97 Grand Prix GT 3.8 using 10W30 and never have had any oil issues or significant usage.
 
quote:

Originally posted by jc1990:
i wish my 92 sunbird 3.1 was like that the engine has 140000 miles run like crap burns oil and gas and the car is just so cheap i hate it also have a 96 grand am 3.1 92000 miles pos typical pontiac sucks

Good points, I was wondering if a Sunbird lasting a long time was a good thing at all.
 
I've been a car nerd for decades (I'm 59) and consider myself well educated on oils. However I'm not nearly as informed on the technical aspects of engine oil as many of you are.

BUT...no one has mentioned the ability of lower-viscosity oils to be pumped, upon cold starts, into bearings quicker than thicker oils. Surely there are SOME reduced-wear advantages to that.

And on selecting perhaps-different-viscosity oils by season, that certainly makes sense to me, if both are within the manufacturer's recommendations, and at least after the first year of so of life. My Porsche Cayenne Turbo has the recommended-for-ALL-temps M1 0W-40. Maybe for the change that will include next summer, I'll go to the 5W-40. But with changes recommended only every 20,000 miles, that's a bit difficult. Maybe I'll change twice a year, before summer and before 'winter'. (I live in Phoenix and we don't have winters here, just 6 months of summer and 3 months each of fall and spring.)

I also have an OilGuard bypass filter mounted but not yet plumbed. This twin-turbod V8 is complex and I don't yet have a (very-expensive) shop manual for it.
 
My thoughts are that it would be very difficult to shear a 20wt oil in the rod and main bearing area of a running engine . Areas like the valve train or timing chain yes . The Engineers probably know this as well and have taken into consideration or designed the the lighter weight valves with reduced spring pressures to control them and fewer engines are using timing chains .

I used 20w/20's all through the 70's in those old OHV dinosaur motors with the valve train turn half the speed of the crankshaft and had nary a problem but went to 30wts when summer came around . Your miles may vary though .

[ December 24, 2003, 05:44 PM: Message edited by: R Stuart ]
 
quote:

Originally posted by Mystic:
Automakers have been recommending 5W30 oil in most new cars/trucks for several years now. And Ford and Honda have been recommending 5W-20. What is the truth about all of this? Is it really better to run 5W-30 throughout the year, including the summertime (or 5W-20 in the case of many vehicles), or is it better to run 10W-30 in the summer?
-*-*-*


Gotta let the climate dictate something. You have to take all factors into consideration.
No oil will be the LOST ARK, not even mine. All things in your application have to be placed into the mix.
Now, there are a few fantastic 5-20 oils. Your call.
If it were me, there are only a few I would run. In my climate I can do that.
Just think about this... THE MFG want to appease someone, and it's not the customer per se... They want to stay in "THE GRACES" for their "WARRANTY PERIODS" where they are liable... after that they don't care too much IMO they want $$$$
 
Valve trains still turn at half of the crank speed . The oil only has to be thick enough to keep the crank and rod bearings seperated , the viscosity needed depends on how the vehicle is operated and the temperatures .The valve train needs the anti wear additives for protection due to the extreme pressures. The big cummins engines used to use 30w oils when I drove truck in the 70's.From my use of syn oils I really never notice a gain in mpg worth mentioning.even wiht Amsoil S 2,000 oil.

[ December 25, 2003, 03:33 PM: Message edited by: Steve S ]
 
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